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H. A. HARVEY.

SCREW.

No. 288,798. Patented Nov. 20, 1883.

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- (No Model.) 2 Sheets-Sheet 2. H. A. HARVEY.

SCREW. No. 288,798. Patented Nov. 20, 1883.

. wzfims Q Q I Juraufiy UNITED STATES PATENT Erica.

HAYWARD A. HARVEY, or ORANGE, New Jersey, ASSIGNOR TO THE HARVEY sonnw AND BOLT COMPANY, or CONNECTICUT.

SCREW.

SPECIFICATION forming part of Letters Patent No. 288,798, dated November 20, 1883.

Application filed January 10, 1883. No model.)

To all whom it may concern.-

Be it known that I, HAYWARD A. HARVEY, of Orange, in the county of Essex and State of New Jersey, have invented anew Improvement in Gimlet-Pointed Screws 5 and -I do hereby declare the following, when taken in connection with accompanying drawings and the letters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this specification.

Figure 1 is a side view of a headed blank as prepared for the rolling and pointing operation. Fig.2 is a side view of the finished screw. Fig. 3 represents a rolled wood-screw having the point conical, and such as made by inventions of my own prior to this present invention. 7

This invention relates to an improvement in that class of wood-screws which are made with a point, and onto which point the thread from the body is continued, to form what is commonly called a gimlet-point, because of its resemblance to boring-instruments which are provided with a screw-point, and by which point the instrument is drawn into the wood, such point on the screw enabling it to be turned into the wood without first boring a hole for its introduction.

In the usual construction of these screws a spiral groove has been out in the body of the blank to produceathread, and this groove continued onto the point. This cutting the groove intothe blank removes a large portion of the metal, and the cut extending onto the point makes it not only difiicult to form a perfect thread on the pointed portion, but very difficult to make the point concentric or in per.- fect axial alignment.

The object of this invention is to overcome these defects and produce a gimlet-pointed screw, not only with the thread more perfect throughout and the point in perfect axial alignment, but to make the screw much stronger than the usual cut screws of this class; and the invention consists in a pointed screw having the spiral rib which forms the thread raised from the body of the blank by the process of rolling, in contradistinction to cutting a spiral groove in the blank, said raised spiral rib extending around the pointed part of the blank.

Before proceeding to a description of my invention it is proper that I should refer to the steps which led me to it. Prior to 1879 I conceived the invention of rolling the threads of screw-blanks between two or more pairs of dies, the first pair being so organized as to form a comparatively shallow groove in the path of the thread around the shank of the blank, and the next pair of dies being so organized as to make such groove deeper either to the extent of finishing the thread or of partially finishing it preparatory to subjecting the blank to the action of a third pair of dies, and so on until the thread of the desired depth is formed. In these pairs of dies one part of each pair is cylindrical and arranged to revolve, the other part of each pair stationary, its face curved corresponding to the face of its revolving mate, and the adjacent faces of the two dies provided with inclined parallel ridges, and so that the screw-blank introduced atone end of the stationary die and parallel with the axis of revolution of the revolving die will be rolled along the surface of the stationary die by the revolving die, and in its passage between the two parts the blank is impressed, the metal thrown out to form the spiral rib, called the thread. Letters Patent of the United States No. 223,730, dated January 20, 1880, were granted to me for this invention. The faces of these dies were parallel with each other, and so that the body of the screw acted upon by the dies was of equal diameter throughout. As this invention would only produce screw-threads of equal diameter throughout, and as it was necessary that a screw should have the capacity of entering wood without previously boring a hole for it, I made the point of the screw conical, as seen in Fig. 3 of the accompanying drawings. This point was sharp and concentric, and while such a screw may be forced into soft wood without boring a hole preparatory to its introduction, such a point has not met the demands of the trade, which has become accustomed to the gimlet-point. While my inventionwould produce screws much more rapidly, cheaply, and better than the established gimlet-point, ex-

cept so far as the point was concerned, Ihave found it necessary to produce a gimlet-pointed screw. To cut the points after the thread has been raised by rolling adds so greatly to the expense of manufacture as to make it impractical. I then conceived the idea of bringing the lower edge of one or more of the pairs of dies together at the point end of the blank,

and continue the ridges on the faces of the' dies over those projecting surfaces, and so that as the blank passed between the dies the ridges on the dies would raise the rib on the blank and continue it down to the point. This improvement in the machine is the subject of an independent application for Letters Patent. By thus rolling the blank between the revolving and stationary dies the rib is continued down to the extreme point, and that point in exact axial line with the body of the screw.

In producing this new gimlet-pointed screw the wire is cut into blanks of suitable length, and the said blanks headed and prepared for threading, substantially in the usual manner, such a prepared blank being shownin Fig. 1. The blanks are rolled between dies which have in their adjacent surfaces diagonal ribs, which, as the blank is rolled between such ribbed surfaces, impress the blank and raise or throw out the metal between the ribs on the die, and such raised or thrown up metal forms a spiral rib on the body corresponding to the space between the ribs on the die. This method of rolling spiral ribs on screw-blanks to form the thread, broadly considered, is not new; but prior to this invention such rolled screws have been cylindrical throughout the threaded portionthat is, of equal diameterand consequently what are commonly called blunt-pointed screws. In this new and improved screw the end of the screw is drawn or wrought into conical or pointed shape, and the spiral rib on the body continued down onto the point by the same rolling operation. The pointed screw thus produced is shown in Fig. 2.

One of the great advantages of this gimletpointed screw over the cut screw is that the process of rolling, which draws down the point and raises the spiral rib thereon as a continuation of the raised spiral rib on the body, not

only brings the pointconcentric-that is, into axialalignment with the body of the screw but prevents the breaking up of the fiber of the n1etal-unavoidablein a cut-thread point and thereby rendering the point of this new screw harder and stronger thanthe cut point can be. Because of the concentric or axial alignment of the point of this new screw, it more readily enters the wood, and requires less power to drive it than the usual cut-thread point.

Another and important advantage of this new screw is that the point may be made sharper than can be done in a cut screw. This sharper point also facilitates the driving or turning the screw into the wood.

The gimlet-pointed screw thus produced is made from wire of smaller diameter than the same diameter of cut threaded screw, for the reason that the rib which is raised from the body of the blank enlarges the diameter of the threaded portion, as seen in Fig. 2, and is not of the same diameter as to neck as in .cut screws, while the diameter of the body of the threaded portionthat is, at thebottom or root of the threadis the same as in the cut screw. The metal is not removed to form the thread, as in the cut screw. The strength of the screw is dependent upon and limited by the body at the bottom of the thread, and not by the diameter of the neck; hence by raising the spiral rib by the rolling process, in contradistinction to cutting the spiral groove, and continuing that spiral rib down onto the pointed portion of the blank, substantially the same size screw is produced by so much less cost of material as the diameter of the blank is less than must be used to produce the usual cutthread gimletpointed screw.

The peculiarities of this raised spiral-ribbed giinlet-pointed screw hereinbefore described readily distinguish it from gimlet-pointed screws as heretofore produced, even to the eye of those unskilled in the manufacture of screws.

From the foregoing it will be understood that I do not claim, broadly, a wood-screw having the spiral rib which forms the thread raised from the body of the blank, whereby the diameter of the thread is greater than the body of the blank.

I am aware of Patent No. 161,529, and claim nothing therein shown or described, that patent lacking the characteristic feature of my inventionto wit, a spiral rib raised from the body and continued around the pointed part of the body, and so as to form a gim1et-p0int the said patent showing rather a cutter and center point than a gimlet-point.

A pointed screw having the spiral rib which forms the thread raised from the body of the blank, in contradistinction to cutting a spiral groove in the blank, said raised spiral rib continued around the pointed part of the body and forming a gimlet-point, substantially as described.

J GEN E. EARLE, J 0s. 0. EARLE. 

